香港大学Shengchao Yu和Jiu Jimmy Jiao的团队研究了全新世珠江三角洲地下水系统的演化历史。2023年3月17日出版的《地质学》杂志发表了这项成果。

课题组将水文地质调查、水文地球化学数据与数值模拟相结合，对珠江三角洲含水层地下水系统的演化进行了评价。课题组研究了晚更新世至全新世区域地下水流动系统中，流动动力学和氧化还原条件对营养物生物地球化学过程的影响，以响应与古降水变化和海水盐度下降相关的瞬态。含水层-弱透水层系统的古水文地质重建结果表明，古海水侵入形成的盐碱化地下水仍存在于旧的海洋弱透水层中，并影响着相邻含水层的地下水盐度和化学物质，而浅层年轻的海洋弱透水层中大部分地下水已被旧/新鲜雨水入渗而焕然一新。

研究结果表明，珠江三角洲总铵和总碳储量分别为(1.91±1.13)× 10⁷ mol m^-1和(5.74±4.05)× 10⁷ mol m^-1，地下水向海洋排放的铵和碳酸氢盐通量分别为(90.6±55.9)mol m^-1 yr^-1和(301.02±196.23)mol m^-1 yr^-1。埋藏在珠江三角洲的铵如释放入海，将相当于珠江近205±123 yr 的河流负荷。这些结果表明，全新世期间沉积在三角洲含水层系统中的化学物质可能导致未来海洋富营养化和酸化。

附：英文原文

Title: Evolutionary history of the groundwater system in the Pearl River Delta (China) during the Holocene

Author: Shengchao Yu, Jiu Jimmy Jiao, Xin Luo, Hailong Li, Xuejing Wang, Xiaolang Zhang, Meng Yao, Jinchao Zuo, Wenzhao Liang, Meiqing Lu

Issue&Volume: 2023-03-17

Abstract: Coastal groundwater reservoirs are sensitive to the complicated evolution of marine transgressions and regressions in river delta regions. We integrated hydrogeological investigation and hydrogeochemical data with numerical modeling to assess the evolution of the groundwater system in the Pearl River Delta’s aquifer system (in southeastern China). We studied the effects of flow dynamics and redox conditions on the biogeochemical processes of nutrients in the regional groundwater flow systems in response to the transient states related to variable paleoprecipitation and seawater salinity decline from the late Pleistocene to the Holocene. The results from paleo-hydrogeological reconstruction of the aquifer-aquitard system showed that the saline groundwater formed by paleo-seawater intrusion was still present in the old marine aquitard and affected groundwater salinity and chemicals in the adjacent aquifers, while most of the groundwater in the shallow young marine aquitard has been freshened by infiltrated old/fresh rainwater. Consequently, total ammonium and carbon stored in the Pearl River Delta were estimated to be (1.91 ± 1.13) × 10⁷ mol m^–1 and (5.74 ± 4.05) × 10⁷ mol m^–1, respectively, and the ammonium and bicarbonate fluxes derived from groundwater discharge to the sea were calculated as (90.6 ± 55.9) mol m^–1 yr^–1 and (301.02 ± 196.23) mol m^–1 yr^–1, respectively. If the buried ammonium in the delta is released to the sea, it would be equivalent to nearly 205 ± 123 yr of Pearl River fluvial loading. These findings suggest that the chemicals trapped in the deltaic aquifer system during the Holocene could contribute to future ocean eutrophication and acidification.

DOI: 10.1130/G50888.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G50888.1/621093/Evolutionary-history-of-the-groundwater-system-inredirectedFrom=fulltext